A memory device having a three-dimensional structure has been proposed, in which memory holes are formed in a stacked body including a plurality of electrode layers stacked therein, and a charge storage film and a semiconductor film extending in the staking direction of the stacked body are provided in the memory holes. The memory device has a plurality of memory cells series-connected between a drain-side select transistor and a source-side transistor. The electrode layers of the stacked body are gate electrodes of the drain-side select transistor, the source-side transistor, and the memory cells. A staircase structure portion in which the stacked body is processed like a staircase is outside of a memory cell array in which the memory cells are disposed. A memory peripheral circuit is electrically connected to the drain-side select transistor, the source-side transistor, and the memory cells via the staircase structure portion. For higher density of the memory device, shrink of the staircase structure portion is desired.